<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

</head>
<body>
<ol>
    <li>
        test1
    </li>
    <li id="li2">
        test2
    </li>
    <li>
        test3
    </li>
</ol>
<script>
    // let o1 = document.getElementsByTagName('ol')[0];
    // let li1 = o1.childNodes[1]
    let li2 =  document.getElementById('li2')
    let next = li2.nextElementSibling


</script>
</body>
</html>